Nine experiments are proposed to further our understanding of the perception of variability between and within social groups. One line of investigation explores the role of visual cues. Experiments 1-3 are designed to demonstrate that the perception of similarity in appearance within groups and of differences across groups may be sufficient to produce the basic facts of intergroup relations: categorization, stereotyping, prejudice, and discrimination. The procedures will involve the creation of arbitrary physical similarities and differences among persons. Experiments 4 and 5 examine the role of visual cues and attributional processes as determinants of whether stereotypes about a group influence the perception of an individual group member. The second line of investigation examines the "psychophysics" of between-group differences. Experiments 6 through 8 explores the causes and consequences of the perception of minority groups as being more criminal than nonminority groups. It is suggested that a small absolute difference between groups in crime rate appear large when the absolute percentages involved are small. Exposing people to the percentages of group members who are "law- abiding" would make minority and nonminority groups appear more similar in criminality. Experiments 9 extends these ideas to the perception of research results, and other applications are suggested as well. All 9 experiments directly bear on the serious social problem of intergroup antagonism, especially the interracial conflicts manifested in the difficulty of achieving integration in housing and education.